This invention relates to heat resistant resin compositions having a low modulus of elasticity, heat resistance and shelf stability and suited as adhesives and sealants for various printed circuit boards and semiconductor packages, and adhesive films using the same.
In concert with the current demand for electronic equipment of smaller size and more multi-functions, the interconnection technology of printed circuit boards and semiconductor packages seeks for a higher density and further miniaturization. As a result, adhesives and adhesive films are required to have sufficiently high heat resistance and low modulus to accommodate the high-temperature process during mounting and relieve thermal stresses upon installation of electronic parts.
In the prior art, low modulus materials were developed by introducing siloxane structures into polyimides and polyamide-imides which are heat resistant resins. These siloxane-modified polyamide-imides are disclosed in JP-A 5-009254 and JP-A 6-116517. However, these resins are less adherent to copper foil and less heat resistant.
JP-A 10-060111 and JP-A 6-271673 discloses to blend a siloxane-modified polyamide-imide with a compound having at least two maleimide groups for improving high-temperature properties. This resin composition is less adherent, especially to copper foil. Japanese Patent No. 3,221,756 corresponding to U.S. Pat. No. 5,677,393 discloses a heat resistant adhesive film comprising a polyimide silicone having phenolic hydroxyl groups and an epoxy resin. Since the phenolic hydroxyl groups are located at sterically dense positions and thus hindered from reacting with the epoxy resin, the bonding effect of hydroxyl groups that arises from the reaction of phenolic hydroxyl groups with the epoxy resin is not expectable.
An object of the present invention is to provide a heat resistant resin composition having improved adhesion, heat resistance, shelf stability and solvent resistance as well as a low modulus of elasticity, and an adhesive film using the same.
We have found that a resin composition comprising the associated product of a polyimide resin having acid anhydride groups in the skeleton with a curing catalyst for epoxy resin, and preferably comprising the associated product, an epoxy resin having at least two glycidyl groups in a molecule and optionally, a curing agent for the epoxy resin cures into a part having a low modulus of elasticity and improved adhesion, heat resistance, and shelf stability. When the composition is applied to a support as varnish, an adhesive film is obtained which is fully adherent to copper foil or the like.
The term xe2x80x9cadhesive filmxe2x80x9d as used herein preferably has a thickness of 5 to 500 xcexcm and encompasses sheets.
Accordingly, the present invention provides a heat resistant resin composition comprising the associated product of a polyimide resin having acid anhydride groups in the skeleton with a curing catalyst for epoxy resin.
Preferably, the polyimide resin having acid anhydride groups in the skeleton comprises the reaction product of an acid anhydride having a functionality of at least 2 with an amine having a functionality of at least 2. The molar ratio of amine/acid anhydride ranges from 0.60 to 0.99.
In a preferred embodiment, the resin composition further includes an epoxy resin having at least two glycidyl groups in a molecule and optionally, a curing agent for the epoxy resin.
Also contemplated herein is an adhesive film comprising the heat resistant resin composition defined above.